Production of carboxylic acids from nitrohydrocarbons



Patented Apr. 12, 1958 UNITED STATES PATENT OFFICE PRODUCTION OFCARBOXYLIC ACIDS FROM NITROHYDROCARBONS Samuel B. Lippincott, TerreHaute, Ind, assignor to Purdue Research Foundation, La Fayette, End... acorporation of Indiana No Drawing.

Application June 14, 1937,

Serial No. 148.107 8 @iaims. ((71. 260-112) 5 actions, but are mosteconomically produced by vapor hase nitration of saturated hydrocarbonsin accordance with the process of U. S. Patent 1,967,667 by H; B. Hess,E. B. Hodge and B. M. Vanderbilt. The nitroparaflins produced bythis 10process from petroleum hydrocarbons. constitute an advantageously cheapsource of aliphatic compounds for the production of organic chemicals. 1have now found that carboxylic acids may be produced from thesenitrohydrocarbons with consistently satisfactory" yields andconversions, by reacting the nitrohydrocarbons with certain mineralacids-under the controlled conditions described below, i

The process of my present invention may be briefly described ascomprising subjecting the primary nitrohydrocarbon at a temperatureabove 110 C. and preferably below 160 C., to the action of from 1 to 3moles of a mineral acid of the group hereinafter set forth, per mole ofnitroacid being at least 75% by weight, and providing either initiallyor at a later stage of the reaction at least 1 mole of water per mol. ofnitrohydrocarbon to complete the conversion to the carboxylic acidstage. According to this reaction 1 mole of hydroxylamine is formed foreach mole of carboxylic acid produced, but the hydroxylv 5 my processconstitute the primary nitrohydrocarbons, as, for example, the primarynitroparafiins, and the aryl or cycloalkyl substituted primarynitroparaflins such as phenyi-nitromethane or 1-nitro-2-cyc1ohexyl-ethane. The primary nitro- 50 paraflins containingtwo or more carbon atoms areparticularly suited fori'se in my process.Among the nitroparamns, nitroethane, l-nitropropane, l-nitrobutane, andl-nitro-Z-methyl propane are particularly advantageous in that theirboiling points constitute suitable reaction hydrocarbon, the initialconcentration ofsaid temperatures, and the reaction mixture may thus besimply refluxed to effect the conversion. It should be distinctlyunderstood; however, that my inventionis not to be limited to anyparticular nitrohydrocarbons of this series, but is generally 5applicable to all nitrohydrocarbons containing the group CH2.NO2.

The acids which may be used to eflect the conversion of thenitrohydrocarbons inmy process comprise mineral acids having adissociation constant in excess of 10- Among these may be mentionedhydrochloric, sulfuric, sulfurous, chlorosulfonic, orthophosph'oric,pyrophosphOric, metaphosphoric, and'nitric acids. It will be evident, ofcourse, that some of these acids will be stitute carboxylic acid andhydroxylamine in approximately equimolecular proportions. I Howeverpwhen a strongly oxidizing acid such as nitric acid is employed, there isa tendency to oxidize the hydroxylamineoandto cause other undesirablereactions. It will also be evident that operating conditions will governthe choice of the acid to be used as the converting agent. For example,it the reaction is to be carried out at atmospheric pressure it isimpossible to secure a sufficiently high concentration of hydrochloricacid, whereas under sufficiently increased pressure hydrochloric acidmay be satisfactorily used. In view of these considerations, and alsofrom the stand- 35,

point of raw material cost, I prefer to-utilize sulfuric acid, but itshould be distinctly understood that my invention is not to be limitedto the use of this particular acid. Any of the mineral acids having adissociation constant in excess of 10" may be used, and one skilled inthe art can readily choose a suitable acid for the particular reactionconditions to be employed.

I have found that the reaction of the present invention proceeds mostrapidly with very concentrated acid solutions, but. that the reactionwill not ,proceed to completion unless 1 mol. of water permol. ofnitrohydrocarbon is. provided in the reaction mixture. Thus, whenemploying anhydrous acids-such as 100% sulfuric 5 r acid, a finalconversion of nitrohydrocarbon to carboxylic acid of the order of is,obtained} but optimum conversion may then be secured by introducing 1mol. of waterfper-mol'of nitrohydrocarbon, and continuing -the reactionuntil 5 When sulfuric acid is'em- 20,

the intermediate products are completely transformed to the carboxyllcacid stage. This final conversion usually requires only from 5 to 15minutes at the reaction temperature. Alternatively, the additional watermay be introduced in a subsequent recovery operation, as, for example,,

, fuming sulfuric acid, may be satisfactorily em- The following resultswere securedz played with resulting saving in time.

A very satisfactory reaction mixture constitutes 1 mol. ofnitrohydrocarbon, and 1 mol. of sulfuric acid in the form of 814.5% acid(constituting 1 mol. of acid and 1 mol. of.water). with this mixture theacid concentration is sufllclently high to give rise to a rapid reactionrate withoutundue dimculty from thestandpoint of heat evolution, and therequisite amount of water for the reaction is present in theinitialmixture so that none need subsequently be added. In general, itmay be said that the preferred acid concentration is that which willgive rise to a rapid conversion rate without unduly rapid evolution ofheat, which will be suillciently miscible with the nitrohydrocarbon toinsure ease of reaction, and which will give rise to a final solution inwhichthe resulting hydroxylamine salt is insoluble. An acid of toconcentration will usually be found to be satisfactory, and preliminaryexperiments will readily determine the optimum concentration for anyparticular acid under the reaction conditions to be employed.

The reaction temperature is preferably maintained between 100 C. and 160C. At temperatures lower than 100? C. the reaction velocity isunsatisfactorily low, and at temperaturesabove 160 C; there is anincreased tendency for decomposition reactions to take place. It will beevident, however, that higher temperatures may My invention may beillustrated by the follow- 7 ing specific examples in which variousnitrohydrocarbons are converted to the corresponding carboxylic acids bythe use of a number of different types of acids as converting agents.

Example I V A reaction mixture comprising 75 'parts by weight ofnitroethane, 98 parts of H2804, and 18 parts of water was refluxed withstirring for approximately 8 hours. The reaction temperature during thisperiod ranged from 113 to 117 C.

. following results were secured:

[sample I! A reaction, mixture comprising 89 parts by weight ofl-nitropropane, 294 parts of H1P04, and 33 parts of water was refluxedwith stirring for 12 hours. The reaction temperature during this'periodranged from 124 to 135 C. The following results were secured:

Yield based on Conversion based Product nitropropane on nitro ropanereacted intro uced Propionlc acid 93% 93% Example III Approximately 89parts by weight of l-nitropropane was added to 108 parts of H1804 whilestirring the mixture and maintaining the temperature at loo-103 C. Thetemperature was then raised to approximately C. and maintained at thatpoint for 50 minutes. At the end of this period 18 parts of water wasintroduced and the mixture was refluxed for 10 minutes.

The following results were secured;

Yield based on Conversion based Product nitropropane on nitropropanereacted introduced Propionic acid Q 92% 85% Example IV A mixture of 89parts by weight of l-nitropropane, 36 parts ofHCl. and 48 parts of waterwas placed'in a pressure vessel and maintained at a temperature of -150C. for 2 hours. The

I Yield based on Conversion based Product nitropropane reon nitrc ropaneacted intro uced Propionic scld. 91% 91% Example V A reaction mixture,comprising 89 parts by weight of I-nitropropane, 82 parts of H2803. and

. 18 parts of water was refluxed with stirring for 8 hours. The reactiontemperature ranged from 128 to C. The following results were secured:

Yieldbasedon Conversionbesed Product nitropropsnereon nitro ropane actedintro uced Propicnicscid,-.-. ..i..-;.-- 00% 02% Example VIl-nitropropane, 63 parts of HNQ:. and 30 parts of water was placed in apressure .vessel and maintained at a temperature of 135-150 Cffor- 4hours. The following results were secured A. mixture comprising 89 partsby weight of Yield'on Conversion based 2 Yisldbesedon CpriversionbssedProduct nitroethene on nitrcethene Product nitrcpropsnereonnitro ropauereacted introduced acted g intr uced somemid-----;;--i- Joey, 86% 5 I-Prbpionieae|d -1... -so% 25% use of any obvious equivalents.

Example VII A reaction mixture comprising 103 parts by weight of1-nitrobutane, 98 parts of H2804, and 18 parts of water was refluxedwith stirring for 2 hours. During this period the reaction temperatureranged from 145 to 158 C. The following results were secured:

Example VIII I Conversion based Yield based on Product nitromethyl gg gg g ggil propane reacted duced I butyric acid 90% 90% It is to beunderstood, of course, that the above examples are illustrative only,and that my in-' vention is not to be construed as limited to theparticular materials or procedures set forth. Numerous modifications ofprocedure will naturally occur to those skilled in the art, and my in:vention includes any such modifications or the the reaction may beadvantageously carried out under super-atmospheric pressure whenemploying any of the mineral acids specified above, and this procedureis not limited in its application to the use of hydrochloric or nitricacids. By increasing the pressure a higher reaction temperature may besecured in the case of the lower boiling nitrohydrocarbons, such asnitroethane, with a resulting increase in speed of conversion. Ingeneral, it may be said that a pressure should be employed which willinsure liquid phase conditions at the reaction temperature utilized.Likewise, it will be evident that my invention can be carried out in acontinuous manner by employing a reaction tube or vessel maintained atthe desired reaction temperature, and passing the reaction mixturesthrough the heated zone at a space velocity sufficient to effect thedesired reaction and minimize decomposition reactions. It will also beapparent that my process is applicable to the treatment of mixtures ofnitrohydrocarbons as well as single compounds, and to the use of mixedacids as the converting agents,

as well as the single acids employed in the above For example.

All such modifications which are not comprises subjecting thenitrohydrocarbon at a temperature in excess of 100 C. to the action offrom 1 to 3 mols of a mineral acid having a dissociation constant inexcess of 10- the initial concentration of said acid being at least byweight, and providing at least 1 mol. of Water per mol. ofnitrohydrocarbon to complete the conversion 'to the carboxylic acidstage.

2. A process for the production of fatty acids from primarynitroparafiins, which comprises subjecting the nitroparaffin at atemperature of 100 C. to 160 C. to the action of from 1 to 3 mols of amineral acid having a dissociation constant in excess of 10', theinitial concentration of said acid being at least 75% by weight, andproviding at least 1 mol. of water per mol. of nitroparaffln to completethe conversion to the carboxylic acid stage.

3. A process for the production of fatty acids from primarynitroparaflins, which comprises subjecting the nitroparafiin at atemperature of 100 C. to 160 C. to the action of from 1 to 3 mols of amineral acid having a dissociation constant in excess of 10- the initialconcentration of said acid being at least by weight, and

. subsequently introducing water to provide a total of at least 1 mol.of water per mol. of nitroparaflin to complete the conversion to thecarboxylic acid stage.

4. A process for the production of fatty acids from primarynitroparafiins, which comprises subjecting the nitroparaflin at atemperature of C; to C. tothe action of from 1 to 3 mols of a mineralacid having a dissociation constant in excess of .10- the concentrationof said acid being such that there is present in the reaction mixture,approximately 1 mol. of water per mol. of nitroparafiin.

5. A process for the production of fatty acids from primarynitroparafiins, which comprises subjecting the nitroparaflin at atemperature of 100 C. to 160 C. to the action of from 1 to 3 mols ofsulfuric acid, and providing at least 1 mol. of water per mol. ofnitroparaflin to complete the conversion -to the carboxylic acid stage.

6. A process for the production of fatty acids from primarynitroparaflins, which comprises subjecting the nitroparaflin at atemperature of 100C. to 160 C. to the action of from 1 to 3 mols. oforthophosphoric'acid, and providing at least 1- mol. of water per mol.of nitroparaflin to complete the conversion to the carboxylic acidstage.

'7. A process for the production of fatty acids .from primarynitroparafiins, which comprises subjecting the nitroparaflin at atemperature of 100 C. to 160 C. to the action of from 1 to 3 mols ofhydrochloric acid, and providing at least 1 mol. of water per mol. ofnitroparafiin to com-

